1. Technical Field
The present invention relates to a lens array substrate, a method of manufacturing a lens array substrate, an electro-optical device, and an electronic apparatus.
2. Related Art
An electro-optical device including an electro-optical material such as, for example, liquid crystal between an element substrate and a counter substrate is known. An example of the electro-optical device can include a liquid crystal device used as a liquid crystal light valve of a projector. In the liquid crystal device, a light shielding portion is provided in a region in which a switching element, a wiring, and the like are disposed, and a portion of incident light is shielded by the light shielding portion and is not used. Consequently, a configuration is known in which a microlens is provided on at least one substrate and light shielded by the light shielding portion disposed at a boundary between pixels, in light incident on the liquid crystal device, is condensed and is made to be incident on the inside of an opening of the pixel to thereby achieve an improvement in light utilization efficiency in the liquid crystal device.
However, the light condensed by the microlens converges, and then spreads radially and is emitted. As an angle at which the light spreads becomes larger, a variation in an angle of light passing through the microlens and being incident on a liquid crystal layer with respect to an orientation direction of liquid crystal is increased. For this reason, there is a problem in that the constrast of the liquid crystal device is decreased. In response to such a problem, a microlens array substrate (counter substrate) is proposed which has a lens layer in which two or more inorganic materials having different refractive indexes are laminated (for example, see JP-A-2007-226075).
In the microlens array substrate disclosed in JP-A-2007-226075, it is possible to improve light utilization efficiency by condensing incident light on the lens layer and to bring emitted light close to parallel light by refracting the light by an interface between a plurality of layers having different refractive indexes. In such a process of manufacturing the microlens array substrate, a plurality of spherical concave portions are formed in a substrate, and sol solutions which are inorganic materials having different refractive indexes are changed into a gel state by being repeatedly applied twice or more onto the surface of the substrate having the concave portions formed therein, thereby forming a lens layer constituted by a plurality of layers laminated. The surface of the uppermost layer in the plurality of layers constituting the lens layer is polished to be flattened, and a transparent electrode and a black matrix are formed thereon, and thus the uppermost layer of the lens layer serves as the surface of the microlens array substrate to form a boundary surface between the liquid crystal layer and the uppermost layer.
Incidentally, in the microlens array substrate disclosed in JP-A-2007-226075, a plurality of layers having different refractive indexes are laminated up to the uppermost layer from the central portion to the end of the spherical microlens. For this reason, incident light may be reflected from the interface between the layers having different refractive indexes at the end of the microlens in which an angle with respect to the surface of the substrate becomes larger, and thus there is a concern of light utilization efficiency being decreased by that amount.
In addition, in the process of manufacturing the microlens array substrate, when the lens layer is formed by laminating the plurality of layers on the substrate having the spherical concave portions formed therein, a concave portion having the spherical concave portion reflected therein is formed in the upper surface of each of the plurality of layers. Accordingly, in order to flatten the surface within a range of a layer thickness of the uppermost layer, the uppermost layer of the lens layer has to be formed to be thicker than the depth of the concave portion of a layer just below the uppermost layer. In addition, since an optical path length of the microlens is adjusted by the layer thickness of the uppermost layer of the lens layer, a predetermined layer thickness (residual thickness) has to be secured while flattening the surface in a process of polishing the uppermost layer of the lens layer, and thus there is a problem in that the optical path length cannot be easily adjusted.